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Abstract

The WENDELSTEIN 7-X stellarator will be capable of running pulses of up to 30 min duration. The control system of W7-X will support all discharge scenarios compatible with this capability, i.e. short pulses with arbitrary intervals, steady state discharges, and arbitrary sequences of phases with different characteristics ("segments") in one discharge. The use of segments substantially reduces the time required for parameter scans and permits short tests of new settings without interfering with the main programme. The hierarchical layout of the control system will reflect the structure of the experimental device. Each technical component and each diagnostic system including its data acquisition will have its own control system permitting autonomous operation for commissioning and testing. The activity of these devices will be co-ordinated by a master control during the experimental sessions. System parameters where relevant to the experiment, will be exclusively controlled by complex software objects. By synchronous changing references to these objects in all computers the whole system behaviour can be modified from one cycle to the next. This allows to switch between segments or to the end of the discharge. The switching may be determined by fixed timing, by logical conditions, or by operator action.